Photographic paper.



A. C. MCCLOSKEY.

PHOTOGRAPHIC PAPER.

APPLICATION FILED MAY 25.19e.

1,265,464. rammed Muy 7,1915.

ALFRED C. MCCLOSKEY, 0F PHILADELPHIA, PENNSYLVANIA, ASSIGNORfBY MESNEASSIGNMENTS, 0F ONE-HALF T0 HIMSELE ONE-FOURTH T0 A. ELTON DAVIS, ANDONE-FOURTH T0 FREDERICK J. GEIGER, ALL OF PHILADELPHIA, PENNSYL- VANI.

rHoToGn'APHrc PAPER.

To all whom it may concern.'

Be it known that I, ALFRED C. MoCLosKEY, a citizen of the United States,residing at Philadelphia, in the county of Philadelphla and State ofPennsylvania, have invented certain new and useful Im rovements 1nPhotographic Papers, of which the following is a specification.

The present invention relates to improvements in that class of paperswhich are sensitized by a coating containing ferrie salts and a gum* orits equivalent, and which are developed by potassium vferro-cyanld andcleared as with sulfuric acid and which produce from tracings or thelike prints having dark lines or marks where the tracms, have dark linesor marks and light groun s where the tracings have light grounds. Theinvention is applicable not onl to such papers when coated upon one si ebut. also to such papers when coated upon both sldes 1n accordance withthe invention forming the subject-matter of my Patent No. 1,213,925,dated January 30th, 1917.

The principal object of my present lnvention is to improve theappearance of the ground by making it more white and entirely free fromstains, and in addition, as applied to my prior invention, to improvethe appearance of the back `in a similar manner, while at the same timethe lines of the print are strong, clear and distinct.

The invention will be claimed at the end hereof but will be firstdescribed in connection with the accompanying drawings forming parthereof and in which- Figure 1, is a diagrammatic sectionalviewillustrating paper embodying features of the invention and coated on oneside only, and

Fig. 2, is a similar view illustrating paper embodying a modication ofthe invention.

Referring to Figs. 1 and 2, the paper 1, has an under coat 2, which willnot dissolve in water or alkaline solutions and which is removable bydilute acids. An example of such a coating is a solution of ferriechlorid/ applied to the paper which when alkaline probably producesferrie hydrate. Pa er which is not alkaline may be given an al alinebath. At any rate the application of a solution of ferrie chlorid to thepaper pro- Speciilcation of Letters Patent.

Patented May 7, 1918.

Application led May 25, 1916. Serial No. 99,712.

duces a coating which does not dissolve or become removable infwater orpotaiumferro-cyanid-the developer-but. which does become removable bydilute sulfuric acid-the clearing solution.- The outer coating 3, mayappropriately contain organic matter, as gum, dextrin, elatin or thelike, ferrie ammonium citrate irown) and ferrie chlorid. Upon exposureunder. a tracing or the like theground, or probably mi-e accurately theexposed art of the outer coating 3, is converted rom the ferrie to theferrous state, and the lines remain in the ferric state, since they arecovered by the lines. of the tracing. The developerpotassiumferro-cyanid-renders the lines insoluble in water and sulfuric acideither by recipitat-ion or otherwise. The ground, ike the under coat 2,is soluble in the acid clearing solution and rendered removable, so thatafter the print is washed 0H" with water the ground is white and freefrom stains, but the back would not. be white if the paper were immersedin the various solutions. To obtain a white back as well as a whiteground and at the same time permit of the immersion of the print in thevarious finishing solutions, which may of course include stainingsolutions in addition to the potassium ferro-cyanid solution, as adeveloper, and dilute sulfuric, or other suitable acid, as a clearingsolution, recourse may be had to the invention of my said prior patentas im'- proved by the present invention. A description will be given ofone manner in which this can be done:

Referring to Fig. 2, the face of the paper is provided with the samesensitizing coating consisting ofthe over and under layers 3 and 2,which is used in connection with the paper illustrated in Fig. 1, andwhich has been above described. Referring to Fig. 2, a coating 2a, offerric chlorid is applied to the other face of the paper so that in thiscase both sides of the paper are provided with an under coat of ferriechlorid. On top of the' coating 2a, and on the back of the paper thereis applied a coating 4, consisting of or containing organic matter asgum, dextrin, gelatin or the like, ferrous ammonium citrate (green), andferrous chlorid.

with the coating 3, and the paper is printed by exposure to light. Allthose parts which are covered b the lines of the tracing remain in' theerric condition but the other arts of the coating 3, which are exposedto the light are reduced to the ferrous condition. At this stage thecoating on the back is the same as that part of the coating on the facewhich has been exposed and acted upon by light. When the print isimmersed in the developing bath containing potassium ferrocyanid, thelines of the print, being ferrie,

l become insoluble in dilute acid either by precipitation or otherwise,Whereas the rest of the coating on both the back and front or faceremains or is rendered soluble by immersion in dilute sulfuric acid, theclearing solution. After the print has been developed and Washed inWater, it is immersed in the clearing A'solution and When again Washedin water all of the coatings come off except the lines of the print,leaving a White stainless ground for the print and a AWhite stainlessback. Where staining solutions are employed to produce, for example,black instead of blue lines on a white ground, the action is the samefor any stains produced by the staining solutions or in fact by any ofthe solutions employed or by impurities therein, come off with the eXosed portion of the coating on the front an the coating on the back. Theunder coating formed by the application to the paper of ferrie chloridsince it is insoluble in Water and alkaline solutions remains in placeuntil the final treatment of the print With the acid clearing solutionand so'this coating plays an important part in protecting the paper fromstains and in removing the same. Furthermore this under coat in no Wainterferes With the operations by Which the lines are printed, developedand, if desirable, stained.

The Word paper is used herein in its ordinary sense and includes linen,tracing cloth or any equivalent material, and the Word tracings includesplates, lms, transparencies and the like.

From the foregoing description it is obvious that changes may be made indetails by substituting equivalents in the application of the inventionto different known papers and printing processes, so that the inventionis not limited in those respects nor other- Wise than as the claims mayrequire.

What I claim is:

1. Photographic paper provided on each side with a ferro under coat andon one side With an outer coat containing ferrie salts and on the otherside with an outer coat containing ferrous salts.

2. Photographic paper provided on one side with a ferro under coat andan outer sensitizing coat containing ferric salts.

3. Photographic paper provided on one side with a ferro undercoat and anouter protective coat containing ferrous salts.

ALFREDO. MCCLOSKEY.

